Involute Spline Names, Symbols, and Relations for ANSI Metric Standard
Term | Symbol | Formula |
30 deg Flat Root 0.5 to 10 module | 30 deg Fillet Root 0.5 to 10 module | 37.5 deg Fillet Root 0.5 to 10 module | 45 deg Fillet Root 0.5 to 10 module |
Pitch diameter | D | mZ |
Base diameter | DB | mZ cos α D |
Circular Pitch | p | πm |
Base Pitch | p b | πm cos α D |
Tooth Thick Mod | es | According to selected fit class, H/h, H/f, H/e, or H/d |
Min Major Diameter Int | DEI min | m(Z +1.5) | m(Z +1.8) | m(Z +1.4) | m(Z +1.2) |
Max Major Diameter Int | DEI max | DEI min + (T + λ)/tan α D |
Form Diameter Int | DFI min | m(Z + 1) + 2c F | m(Z + 1) + 2c F | m(Z + 0.9) + 2c F | m(Z + 0.8) + 2c F |
Min Minor Diameter Int | DII min | DFE + 2c F |
Max Minor Diameter Int | DII max | DII min + (0.2m 0.667 - 0.01m -0.5 ) |
Circ Space Width Basic Min Effective Max Actual Min Actual Max Effective | E bsc EV min E max E min Ev max | 0.5πm 0.5πm EV min + (T + λ) EV min+ l E max - λ |
Max Major Diameter Ext d | DEE max | m(Z + 1) - es/tan α D | m(Z + 1) - es/tan α D | m(Z + 0.9) - es/tan α D | m(Z + 0.8) - es/tan α D |
Min Minor Diameter xt | DEE min | DEE max - (0.2m 0.667 - 0.01m -0.5 ) 2 |
Form Diameter External | DFE | 
| | | |
Max Minor Diameter Ext d | DIE max | m(Z - 1.5) - es/tan α D | m(Z - 1.8) - es/tan α D | m(Z - 1.4) - es/tan α D | m(Z - 1.2) - es/tan α D |
Min Minor Diameter Ext | DIE min | DIE min - (T + λ)/tan α D |